Constrained Application Protocol (CoAP) Vilen Looga, M.Sc. Doctoral

Transcription

1 Constrained Application Protocol (CoAP) Vilen Looga, M.Sc. Doctoral

2 Outline Introduction CoAP at a glance Messages Observe Hardware Demo MAMMOTH Conclusions References

3 50 billion connected devices Image by Ericsson

4 Machine to machine (M2M) Image by NXP Semiconductors

5 Machine to machine (M2M) Image by Schneider Electric

6 Node hardware Zolertia Z1 (Contiki OS) Arduino Images by Zolertia and Arduino

7 Node hardware Limited resources: 8KB RAM, 92KB ROM, 16-bit CPU Wireless communication: 6lowPAN over , GPRS, 4G Long-lasting battery

8 Event-driven networking

9 Constrained Application Protocol (CoAP) Application level protocol over UDP Designed to be used with constrained nodes and lossy networks Designed for M2M applications, such as home and infrastructure monitoring Built-in resource discovery and observation RESTful for easy interfacing with HTTP Multicast support Low overhead and simple

10 Request/Response model Client CON [0x11aa]! GET /temp! (Token 0x66)! ACK [0x11aa]! Server Client NON [0xabc1]! GET /temp! (Token 0x76)! Server CON [0xc123]! 2.05 Content! (Token 0x66)! 23.9 C! NON [0xbbaa]! 2.05 Content! (Token 0x76)! 23.9 C! ACK [0xc123]!

11 CoAP message UDP packet SRC port DST port Length CRC CoaP MSG CoAP message Ver T OC Code Message ID Option Delta Length Value Payload

12 CoAP message :4c 9b 2e:77:65:6c:6c:2d:6b:6e:6f:77:6e 04 63:6f:72: Ver. 1 Type 0 Options 2 Request Message ID 0+9=9: Uri- Path Length 11.wellknown 9+0=9: Uri- Path Lengt h 4 core

13 Message types Confirmable (0) Non-Confirmable (1) Acknowledgement (2) Reset (3)

14 Message Code Request (1-31) Response (64-191) Empty (0)

15 Options 1 If-Match 3 Uri-Host 4 ETag 5 If-None-Match 7 Uri-Port 8 Location-Path 11 Uri-Path 12 Content-Format 14 Max-Age 15 Uri-Query 17 Accept 20 Location-Query 35 Proxy-Uri 39 Proxy-Scheme 60 Size1

16 RESTful protocol GET /node-xxx/a/relay -> 1 GET /node-xxx/s/temp -> 22 /node-xxx/a/relay: 1 /node-xxx/s/temp: 22 POST /node-xxx/a/relay/1 -> OK DELETE /node-xxx/a/relay -> OK

17 CoAP to HTTP proxy /node-xxx/a/relay: 1 /node-xxx/s/temp: 22 CoAP UDP HTTP TCP

18 Resource discovery /.well-known/core /a/relay GET /.well-known/core -> </a/relay>;rt= Relay";ct=0, </s/temp>;rt="temperature";ct=0 /s/temp

19 Observe functionality Observe /s/temp /.well-known/core /a/relay /s/temp Notification 1, 22.5 C Notification 2, 22.9 C Notification 3, 22.6 C

20 Multicast One-to-many has obvious application in IoT networks: Data and code dissemination Delivering event data to a set of interested servers Measurement data to more than one subscriber Current multicast proposals have drawbacks: SMRF: one-way directional flooding; only useful for data flowing from border router to nodes PIM-WSN: too many forwarding states inherited from PIM-SSM alleviated by Bloom filters

21 Multicast Our proposal (Deng Y., Doctoral student): Any node can be the sender Interoperability with outside domains Link layer broadcast One network interface per node RPL (Routing protocol for Low-power and Lossy networks): Uses tree structure Multicast messages can be sent in RPL control messages

22 Proxy Proxy-URI: coap://domain.fi: 60001/node-00x/s/temp/ Uri-Host: domain.fi Uri-Port: Uri-Path: s Uri-Path: temp Uri-Query: // /.wellknown/core /.wellknown/core /a/relay /s/temp /a/relay /s/temp

23 Security Similarly to TLS used in HTTP (-> HTTPS), CoAP is secured using Datagram TLS (DTLS) DTLS = TLS + features to deal with unreliability of TLS: DTLS records are independent: if record N is lost N+1 can still be decrypted, while N is retransmitted TLS handshake breaks if the packets are out of order; DTLS queues handshake messages until the correct one Application is responsible for dealing with packet reordering, loss, data re-assembly etc. Minimal implementation of MUST configurations: Not all cipher suits supported DTLS does not work for multicast communication Devices should keep connection open as long as possible to avoid mutual authentication setup overhead

24 Resource directory /a/relay /s/temp /domain.fi/node /a/relay -- /s/temp /domain.fi/node /a/relay -- /s/temp /a/relay /domain.fi/node /a/relay -- /s/temp /s/temp /.wellknown/core /.wellknown/core /.wellknown/core /a/relay /s/temp Application Application

25 NanoService Platform Demo

26 P2P Resource Directory Image by Meirong Liu

27 Hardware Tiny CoAP sensor by Ericsson Research Ethernet, IPv6, UDP 48 lines of assembler code Does not support Observe Image by Ericsson

28 Implementation Software Type Supported Platform libcoap Client, Server x86, Contiki, tinyos Californium Client, Server Java Copper Client Javascript Erbium Client, Server Contiki and many more

29 MAMMOTH: Large-scale IoT demo

30 MAMMOTH Architecture 20 million nodes Proxy per 2k nodes Node traffic going to balancer, which forwards to backend Apps and services can connect to the backend (resource directory)

31 References IETF CoAP draft: IETF CoAP Observe draft: Jari Arikko. Tiny CoAP Sensors. DTLS: More than 50 billion connected devices taking connected devices to mass market and profitability (whitepaper). Ericsson Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, Cisco

32 Thank you! Questions?